The present invention relates generally to primary packaging and more particularly, to packages formed from polymeric films which are heat sealed to paper and/or non-woven materials to produce peel-open packages.
The use of heat sealable polymeric films is widely used in the packaging art. Direct heat sealing between polymeric films and paper or non-woven materials such as DuPont™ Tyvek® and the like, is attractive commercially because they can be formed by directly fusion heating of the outer surface of polymeric film to the paper or non-woven material. However, gaining access to articles which have been packaged by heat sealing films to themselves or to other substrates often presents problems due to the strengths of the seals which are produced. The force required to open the package must be comfortable for the end-user but still strong enough in order to avoid the accidental opening of the package during transportation, handling and storage of the same. For example, if the seals are to have sufficient strength to maintain their integrity, upon opening of the package, the sealed area of the package may exhibit linting, i.e., the release of loose fibers from paper or non-woven material resulting from peeling the polymeric film from the paper or non-woven material. Linting can especially be a problem in a sterile environment such as an operating room where the loose fibers can come into contact with a patient. For this reason, direct fusion seals between polymeric films and paper or non-woven materials for medical packaging applications must be provided without substantial release of free fibers when the package is peeled open.
This problem can be addressed by constructing polymeric films so that they fail within their respective structures when a peeling force is applied, such failure being by delamination of a multilayer polymeric film or by rupture within the thickness of a layer of the polymeric film. However, this film construction will often still result in high peel strengths which cause linting or tear in the paper or nonwoven. For applications where linting or tear is problematic, a coated paper or nonwoven is used. This method allows the applied coating to fail cohesively during peeling of the seal area, protecting the paper or nonwoven surface from linting or tear. However, coated paper and coated non-woven materials are significantly more expensive than their uncoated counter-parts.
Therefore, there is a definite need to provide direct fusion seals between polymeric films and uncoated paper or uncoated non-woven materials without experiencing the problems discussed above.